In making optic fiber cable, a cladding is used around the central core for protecting and improving the operation of the optic signal passing through the cable. Significant efforts have been made to optimize the physical and operating characteristics of the cladding beyond its general purpose of protecting the core of the cable. In the past, the cladding has been made by various materials, such as quartz powder which are highly purified to drastically reduce impurities occurring in natural quartz powder. Quartz powder was employed because it was relatively inexpensive and provided great physical properties when it had an even particle size distribution and was highly purified, such as IOTA 4 powder sold by Unimin Corporation of New Cannan, Conn. Such commercially available, highly purified, naturally occurring quartz powder was physically excellent for cladding, but did not result in the best attenuation of the cladded cable. Indeed, the attenuation was greater than 0.190 dB/km, a level not generally wanted in the industry. The present invention relates to a modification of the commercially available, highly purified, quartz powder, which modification results in a quartz powder that causes vastly improved attenuation and, indeed, has a reduced attenuation at a level of less than 0.187 dB/km and preferably at a level below the targeted attenuation value of 0.184 dB/km. Consequently, by the modification of the highly purified quartz powder in accordance with the present invention, this modified powder is now not only well designed to be used in the optic fiber cable industry, but also causes cladding using the new quartz powder to have improved attenuation properties.
As background to the present invention, the highly purified quartz powder, which is the starting point of the present invention, is a powder of the type marketed by Unimin Corporation under the trademark IOTA, preferable IOTA 4 or alternatively IOTA 6, which often is made from IOTA 4. To create this background powder, the naturally occurring quartz is ground and sized into a powder typically at having about a 100 screen size and has a low level of naturally occurring lithium in solid solution, which lithium remains after the high purification process. The quartz particles of the natural silica are purified so the particles have only a minute level of natural occurring impurities. Indeed, the processing reduces the impurities combined with the SIO2 particles to the lowest level commercially practical, such as less than 0.3 ppm lithium and generally about 0.2 ppm lithium. This is the background material of the present invention. This material is modified to render a “new” powder with an increased amount of lithium in solid solution, which new powder is used for the cladding of optic fiber cables. It creates an attenuation value not heretofore obtained by the commercially available highly purified quartz powder.